Grey Cards .... erk!!!
Well, gang, as you may or may not know ., my very most favorite color paper - IlfoColor - has been discontinued, according to the Ilford web site. In its place, Ilford lists a "NEW!!!" color paper designed expressly for use in automated digital machinery, and is processed using RA-4 chemistry. Depending where one lands on the Ilford web site, this is either "suitable for use in conventional optical equipment" or, "NOT suitable for conventional optical equipment" (!?!?!?). Either statement appears to carry the same amount of weight ... so, being adventurous, and possibly not as sensible as I should be ... (possibly?) ... I'm going to give it a shot, when and IF I ever see it.
The situation is not much, if at all, better with Fuji papers. Same "suitable - not suitable" contradictions. A major trouble with Fuji is trying to delineate one paper from another. They have labelled their Crystal Archive paper in various ways, "Type C", "Type C5"; Type "C8"; Type "P" and "MP, and ... I have *no idea what the differences are. I'm wringing out Fuji "CDII" - go ahead, ask ... I will pre-answer: - No, I don't have foggy idea one about what it is - or is supposed to be - like.
1. It is NOT Ilfocolor. The color balance is different. Not better or worse - but different.
2. It is about one stop faster.
3. It is a "grade" (if there was such a thing in color paper) or so "harder", and less forgiving of exposure variations.
More to come later.
NOW!!! The reason for the header above:
In wringing out the Fuji paper, I jury-rigged a target; a page from Ittens "Theory of Color", flanked by two (2) grey cards; one an older, KODAK and a newer "Delta - Last Grey Card You'll Ever Need".
Lo and behold... THEY ARE DIFFERENT!!! The Kodak card requires, on the average, 9cc less yellow color filtration (Omega DA5500), and one half to one stop more exposure to produce an area on the print that will have equal amounts of Cyan, magenta, yellow and the same density as that exposed to the Delta card!
Ha!! Not only that, but HAH!!!! I have always accepted a grey card as being "accurate" but this would indicate a lack of calibration to some grey standard. I have no idea which is correct.
I've always just grabbed a grey card - I have three or four of them - without giving them much thought. I'm THINKING now ... I'm thinking!! Where - has anyone seen a CALIBRATED grey card?
Additionally, I exposed a couple of frames with a "fair caucasian skin" target - my wife ... and I am certain that 9cc of color filtration DOES make a difference.
More to come later, as I wade through the assumptions I've made. Suffice it to say that I have one or two fewer today.
Ed Sukach, FFP.
If you have one watch you know the time. If you have two you're never sure?
A grey card is supposed to reflect a certain amount of light I think. Does that really imply any colour? Could you make a grey card pink and have it reflect 18%? Don't know.
Plus don't they fade? I try to keep my card in the dark when not in use.
But do the cards produce the same black and white density? I always thought grey cards were calibrated for black and white exposure calculations, not for color correctness. I can certainly imagine lots of color combinations that would give you the same grey level when measured by a "color blind" light meter.
[Edited: Nick, you beat me to the punch!]
Both cards were exposed together, in the studio, with Dynalite MX1000 packs and #2040 heads. I too, keep my cards in dark storage ... although not critically.
They are "grey". By definition Grey is equal parts of cyan, magenta, and yellow (a.k.a. "white") at a reflectivity of 18%. If the card reproduces as grey, by the same terms, the color balance should be somewhere near.
If a grey card DOESN'T reflect "18%", of what use would it be in black and white photography?
Ed Sukach, FFP.
Aren't all light meters color blind? I think so. They measure luminance and when measuring a gray card you expect them to read an 18%. You could have a Blue Card or Red Card as long as they reflected 18%, they would reflect middle gray.
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I agree! My wife, a graphic artist/illustrator/painter, can seemingly differentiate more colors than we mere mortals even think exist. I've long since learned to stop saying anything was grey. She'll say "No, it's _________!"
Originally Posted by chuck94022
My thinking is a grey card is primarily used for exposure. But if you think about it, in a color situation, it'll take fairly precise filtration to replicate the grey color of the gray card in a color print exactly.
Ed, it's an interesting observation, and I'll be watching this thread to satisfy my own curiosity.
"Often moments come looking for us". - Robert Frank
"Make good art!" - Neil Gaiman
"...the heart and mind are the true lens of the camera". - Yousuf Karsh
Exposure was not a factor. It HAD to be nearly equal on both sides of the frame, the shutter was only fired once. I was trying to determine difference between grey cards - or if there was any. There is!
Are exposure meters "color blind"? In a perfect world, they are... Are they in truth ...? Good question! I can't remember ever seeing a spectral sensitivity graph ... which proves nothing. The sophisticated cascade photometers we used (in a different life) were more or less color-blind, really measuring radiated energy ... but that has little to do with a run-of-the mill exposure meter.
Even if the response of the exposure meter is not chroma dependant, black and white film certainly IS -- see Fred Picker and his modified meters.
Hmm ... I need a tri-axis reflectance color spectrophotometer .. that will read "fair caucasian skin" as well as paper images. Think I'll find one on eBay?
In the meantime, it is "investigate and improvise" time.
Ed Sukach, FFP.
As you're aware, not all meters have the same spectral sensitivity, as they have different sensor material. I'm no expert, but I understand that some are filtered back closer to even spectral response differently by different manufacturers, so an 18% blue won't meter the same as 18% green or 18% red across different meters. If you want that, you'll need a color meter. Seems that I read recently that Sekonic went for 15%, but I don't know how reliable that information was. But, as I understand it, the point is that a given color (especially a very saturated color) that reads as 18% reflectance on a selenium cell won't read the same as on a CdS cell, a gallium arsenide cell, or even another selenium cell meter made by another manufacturer. The closer to neutral (equal RGB reflectance) the standard 18% target is, the better.
Just as you are using them, the gray card is not only to meter from, but also to be used to filter for the same color in the final print. Theoretically, the filter pack that puts your Kodak gray card back at proper rendition will also put the Delta last gray card at the proper density and color balance, but no film/print material is perfect, so you just get acceptably close, depending on the materials and your preferences. (BTW, my properly stored Kodak gray cards have long outlasted the Delta Last Gray Cards I bought. The coating on the Deltas all went sticky and gooey and will now smudge and transfer to your fingers.)
There are other standards, like the Gretag Macbeth Color Checker and Kodak color separation guides, that have a gray scale and some standard color swatches to check color replication. (I can't mention here that my computer imaging program, Picture Window, will take a scanned shot of a Macbeth color checker or the gray scale in a Kodak Q-13, align to the swatches, and then massage the numbers to correct color balance and density.) I've found the Macbeth very useful for determining filtration for color transparency films and for color correcting prints in the darkroom.
Last edited by Lee L; 03-15-2005 at 02:36 PM. Click to view previous post history.
This is a *crappy* scan of the makeshift target. Exposure was determined with a Gossen Ultra-Pro meter in "flash" mode, with Studio attachment.
Last edited by Ed Sukach; 07-27-2007 at 08:31 AM. Click to view previous post history.
Ed Sukach, FFP.